The present invention relates to the field of sensitive manufacturing processes that require, at least in part, a contaminant-free environment. More specifically, the present invention relates to the field of cathode ray tube manufacture, particularly the processing of cathode ray tube funnels after an interior coating has been applied. The present invention provides a system and method for better ensuring that no contaminants lodge in a cathode ray tube funnel after an interior coating has been applied, but before the tube is sealed.
Cathode ray tubes (xe2x80x9cCRTsxe2x80x9d) are used in most television sets and computer and video monitors. A typical CRT is illustrated in FIG. 1. The CRT (100) is a glass tube with a bottle-like shape in which a relatively flat bottom portion (101) narrows into an elongated neck portion (102). The relatively flat portion (101) of the CRT (100) becomes the screen on which the display of the television set or monitor is generated when the CRT is incorporated therein. An electro-luminescent material, such as phosphorus, that emits light when struck by an electron beam, is coated over the interior of the screen portion (101) of the CRT (100).
An electron gun (not shown) is then installed in the neck (102) of the CRT (100).
A stream of electrons emitted from the electron gun is scanned over the electro-luminescent layer and turned on and off during the scanning to cause the electro-luminescent layer to glow in certain places and not others. In very simple terms, this is how an image is generated on the screen of a television or video monitor.
A yoke (not shown) is provided around the neck (102) of the CRT (100). This yoke produces a changing magnetic field through which the electron beam from the electron gun passes. The electron beam is deflected by the magnetic field of the yoke. Consequently, by varying the magnetic field created by the yoke in a precise cycle, the electron beam can be scanned, line-by-line, over the entire surface of the screen to generate video images thereon.
It is very important to ensure that no dust or other contaminants are allowed into the CRT (100) during its construction. Contaminants that remain in the CRT (100) when it is operating can degrade the performance of the CRT (100) and even cause damage to the tube by, for example, intefering with the operation of the electron gun and the emitted electron stream.
A cathode ray tube is generally constructed in the following matter. The neck (102) or funnel portion of the CRT (100) is formed open at both ends. Then the relatively flat bottom, or display portion (101) is sealed to the large end of the funnel and the electron gun is installed in the narrow end or neck of the funnel.
The display portion (101) is sealed to the funnel (102) using frit. Frit is a glass paste that can be cured or hardened. Frit (103), in paste form, is applied around the large end of the funnel (102) between the funnel (102) and the display portion (101). The frit is cured or hardened to form a frit seal (103) between the funnel (102) and the display portion (101).
Before the funnel (102) and display (101) portions are sealed, coatings are applied to the interior of the funnel (102). These coatings including carbon material necessary to the optimal operation of the CRT (100).
Obviously, while working with the open funnels to apply the necessary interior coating before the tubes are sealed with a display portion, contaminants, such as dust, moisture, particulate matter, etc., can be introduced to and lodge in the open funnels. As noted above, this contamination can degrade the performance of the finished CRT.
Consequently, there is a need in the art for systems and methods that will minimize or eliminate contaminants that may be introduced into cathode ray tubes during manufacture. In particular, there is a need for an improved system and method of preventing any such contamination from being introduced into the open funnel of a cathode ray tube after interior coating has been applied, but before the tube has been sealed closed.
The present invention meets the above-described needs and others. Specifically, the present invention provides an improved system and method of preventing contaminants from being introduced into the open funnel of a cathode ray tube after an interior coating has been applied, but before the tube has been sealed closed.
Additional advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The advantages of the invention may be achieved through the means recited in the attached claims.
The present invention may be embodied and described as a system for minimizing contamination of cathode ray tube components during manufacture. The system preferably includes a shielded transport path that prevents contaminants from reaching components of cathode ray tubes moving in the transport path, where a first end of the shielded transport path receives the components of cathode ray tubes from a first workstation; and a second end of the shielded transport path outputs the components of cathode ray tubes to a second workstation.
In a particularly preferred embodiment, the shielded transport path is a transport path enclosed in a tunnel. The tunnel preferably includes at least one access door for accessing the enclosed transport path in the tunnel. The tunnel may also include an intake for a vacuum system used to clean the tunnel.
In a preferred embodiment, the cathode ray tube components are funnels; the first workstation is a carbon coating application station; and the second workstation is a drying oven tunnel through which the transport path is routed. This is a particularly contaminant-sensitive portion of the manufacturing process that would benefit from application of the present invention. In such a case, the transport path would preferably be a conveyor that transports pallets, each of which supports one of the funnels.
The present invention also encompasses the methods of making and using the system described above. More specifically, the present invention may encompass a method of minimizing contamination of cathode ray tube components during manufacture by shielding a transport path with shielding that prevents contaminants from reaching components of cathode ray tubes moving in the transport path, where a first end of the shielded transport path receives the components of cathode ray tubes from a first workstation; and a second end of the shielded transport path outputs the components of cathode ray tubes to a second workstation. The method preferably includes shielding the transport path by enclosing the transport path in a tunnel.
The method may also include providing at least one access door in a side of the tunnel for accessing an interior of the tunnel. The method may also include cleaning the interior of the tunnel to remove contaminants. This may be performed by operating a vacuum system connected to the tunnel.